GPX vs TDI


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Got out with a good friend this past weekend to do a bit of testing.

We went to a patch that has produced both shallow and deep nuggets and almost zero trash. Both units were fitted with the same coils. 12" round mono.

This Northern Nevada location is next to an ancient inland sea, bedrock is limestone, soil is very alkaline. Salt was mined nearby.

GPX vs TDI. We all know that the TDI was not made to compete with a GP. It's offered as a worthy alternative at less the half the price.

The method we agreed upon was that we would both hunt for targets then mark them with orange flagging.

After three hours of hunting TDI 4 targets, GPX 9 targets.

Then we crossed checked targets GPX all of the TDI's targets, TDI 3 of the GPX's targets.

Then we dug. 3 of the TDI targets were sub gram nuggets @ less then 5 inches 1 was a bit of copper from a 22 slug near surface.

Of the 6 targets that the TDI did not hit on all were gold (except 2 more tiny surface 22 lead bits) that were 9" + in depth average size .7 gram the three the TDI did hit on all were less than 6" deep and averaged .4 gram.

FYI the TDI operator has used Fosters designs since the GS2.

All in all it was a great day I got to try out the TDI and can attest to it's ability to find gold. While it cant match the GPX's depth ( and rock steady threshold ) it's a very capable PI detector.

So at less the half the price it found less then half the gold then the GPX.

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Nevada Chris... Good post, it shows a lot of effort; I'm impressed!... It is nice

to be beeping gold... no matter the machine used... We used to live in Lovelock.

475 13th Street... I worked at Eagle Picher. The last time I drove by the house

it was being spiffied up.

More questions...

What headsets were used? Any Boost? You mention both were using the round 11-inch

mono... was it the minelab coil? I guess the standard TDI coil was not tried?

The standard coil for the (now obsolete) TDI is the dual round 12-inch mono.

Which version of the TDI? The latest version of the TDI is claimed to be improved

over the original version... The standand coil for this new versio is said to be

a non-dual 12-inch mono.

Best... "Tailgate" Jim Straight

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HI Jim,

Lot's of the homes in Lovelock are getting spruced up. EP is still letting the dust fly.

Detector Pro Black Widows, No amp, NF Advantage 12" round mono (it's the only coil we had 2 of) James did switch back to the stock coil for the rest of the day said it was easier to pinpoint with. Oh another thing he mentioned was the edge of the coil was hot.(the NF)

TDI was purchased 2 months ago. All I know is it was not a "Pro" GPX is over a year old.

Also the TDI had no problem with GB and was as smooth as a GP3000 more or less.

Next time were going to play with the discrimination.

:waves at Rudy::

nvchris

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Nice work Chris...taking time from pure nugget hunting to cross test detectors is generous of you and helpful to others.

Long ago someone down in Australia did some extensive comparisons of his Goldbug finds versus the Minelab 2100 or 2200...the finds were proportional to the costs of each machine,ie; his 500 dollar machine found 1/4 as much as the 2000 dollars machine...this is a very rough recap from a weakening memory...

The point is that there is good value in machines like the TDI...plus the TDI is excellent for hunting old coins and hunting on the beach which gives it a broad appeal to those that can't live on the gold-fields...

Still, for getting small, deep and most of the nugget gold available the PI Minelabs are the best...in my opinion.

fred

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Hello NvChris,

I think that is a very fair evaluation of the TDI. I used the TDI at Moore Creek the first time when it first was introduced. I also spent some time here in Arizona with one at Rich Hill and the Bradshaw area. Found a few small nuggets with it, but when you're so used to what a Minelab PI can do, it was tough to stick with it.

Talk with you later,

Rob Allison

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Excellent post Chris, out of curiosity what timings where you using on the 4500? I assume it was Sensitive Xtra. My experiences with the TDI here in Australia were not as favourable for the TDI mainly due to the extreme mineralisation where it was difficult to get an accurate ground balance and also a lack of decent depth and sensitivity over the ground we have here, so I think the ratios would be somewhat different in my conditions. :blush: To be fair though I only had a very short time with the TDI so these are my early impressions, but I do have a GS5B at my disposal which I have played around with on a more regular basis. (I'm a bit of a metal detector tragic :lol: )

JP

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Gosh... the TDI being compared with the GPX is no longer

being manfactured. It is being replaced by the TDI Pro.

And likely the GPX will be replaced by another update.

(Hah, ha NVChris... I hope the "dust" is not flying at EP. this was a problem when I worked at Kennecott in McGill and also for Kaiser Steel in Fontana)... sorry

I cannot resist mentioning this as Kaiser Steel and the

Kennecott Nevada are both gone).

I like what is being posted... Nice and friendly with good information...

Jonathon Porter... I have followed most of your posts

and I have learned from them...

This goes with everyone else who have posted... Keep em coming... I have access to both the GPX and the TDI and

am glad to learn more good stuff... Thanks

Tailgate Jim Straight

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Jim,

Thanks for the update! I'm sure plenty of folks are anxious to get there hands on the TDI Pro model. Whites definitely has a proven platform to build on.

You being an ex EP worker/miner can attest to the health concerns posed by diatomite getting blown to the four corners.

Jonathan,

Spot on as usual, I did try the Salt/Course timing as well and was surprised by the results (salt was mined right by this secret no longer patch).

Got ant tips for hunting salt flats?

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Jonathan,

Spot on as usual, I did try the Salt/Course timing as well and was surprised by the results (salt was mined right by this secret no longer patch).

Got ant tips for hunting salt flats?

If the conductive component of the ground is extreme (manifests itself as a constant moaning sound) then try a DD coil in Cancel mode, the out of phase nature of Cancel mode will deal quite effectively with the conductivity, if the ground is also mineralised then you can also use Enhance with the GB set on fixed. It is OK to use Enhance when a DD coil is set to either Mono or Cancel mode as DD's are much more sensitive in these modes. Also I would suggest if using Cancel mode to select Inverted on the Response setting in the menu that way small targets will give the traditional High/Low response.

Hope this helps,

JP

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Guest GoldProspectinginOz

With Gs5c (stick to 100 u sec tx) you can deal with conductive ground to some extent with a mono coil by increasing the sample delay from 10 usecs or by using an anti phase coil (salt or anti interference coil) and experimenting with running with either the ALL/high/or low conductivity modes (but you must GB in All mode) and invert or normal audio. The gain may probably also have to be reduced. You can also run a DD on the Gs5c if you increase the sample delay (you may need 17 usecs or more) until you get a stable threshold.

hope this helps,

doug

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Good info Chris. I'm curious as to where your settings were on the TDI. Gain, GB, Conductivity. Did you even attempt to turn off the GB and test some of the targets the TDI couldn't hear? Or did the ground make it impossible to even try?

Digger Bob

Got out with a good friend this past weekend to do a bit of testing.

We went to a patch that has produced both shallow and deep nuggets and almost zero trash. Both units were fitted with the same coils. 12" round mono.

This Northern Nevada location is next to an ancient inland sea, bedrock is limestone, soil is very alkaline. Salt was mined nearby.

GPX vs TDI. We all know that the TDI was not made to compete with a GP. It's offered as a worthy alternative at less the half the price.

The method we agreed upon was that we would both hunt for targets then mark them with orange flagging.

After three hours of hunting TDI 4 targets, GPX 9 targets.

Then we crossed checked targets GPX all of the TDI's targets, TDI 3 of the GPX's targets.

Then we dug. 3 of the TDI targets were sub gram nuggets @ less then 5 inches 1 was a bit of copper from a 22 slug near surface.

Of the 6 targets that the TDI did not hit on all were gold (except 2 more tiny surface 22 lead bits) that were 9" + in depth average size .7 gram the three the TDI did hit on all were less than 6" deep and averaged .4 gram.

FYI the TDI operator has used Fosters designs since the GS2.

All in all it was a great day I got to try out the TDI and can attest to it's ability to find gold. While it cant match the GPX's depth ( and rock steady threshold ) it's a very capable PI detector.

So at less the half the price it found less then half the gold then the GPX.

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Thanks for the tips JP :)

Bob,

Thanks for Jumping into this post, As a Whites dealer/tester maybe you can tell us more about TDI Pro availability.

If my memory servers me, setting were, GB on, GB 7, Freq. around halfway, PD 10, Gain 7, and Low tone.

I ran the TDI after the testing and only messed with the gain and GB knobs. It seems to run most stable at near the halfway marks.

Glad I had a spare Oweegee bungee and Hipstick that thing is heavy.

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Thanks for the tips JP :)

Bob,

Thanks for Jumping into this post, As a Whites dealer/tester maybe you can tell us more about TDI Pro availability.

If my memory servers me, setting were, GB on, GB 7, Freq. around halfway, PD 10, Gain 7, and Low tone.

I ran the TDI after the testing and only messed with the gain and GB knobs. It seems to run most stable at near the halfway marks.

Glad I had a spare Oweegee bungee and Hipstick that thing is heavy.

Well, the TDI Pro is available now. Any dealer that wants one can order one. Unless Jimmy has sold out his entire stock, you can get one. I've only seen one tested in the field but didn't use it as I was using mine at the time. So, I can't give an evaulation or comparison yet. Yes, they are a bit heavy. Not bad if you are on flat ground but hunt a hillside and it's tiring pretty quick.

When you say Low tone, I think you mean Low conductivity which gives you a high tone. This is the preferred setting for smaller nuggets, which is what you were finding. And yes, it is most stable with the gain about 6, halfway. With practice you can run higher but need to listen more closely for those faint targets. And the Pulse was set right at 10.

I was curious if you tried it in the "All" setting which can sometimes give a bit stronger response to weak targets. But the biggie is if it was tried with the GB turned off, just to test some of the targets the Minelab heard but the TDI didn't. GB off will definatly give you more depth and could bring a no sound to within hearing range. But, you can't hunt like that unless the ground will allow it. It was just a testing question to see if could be heard by tweaking the controls.

Digger Bob

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Bob,

I spoke to James about the settings he used and this post tonight.

No he did not try it with GB off or the all setting. The point of the test was to use the setting that you would hunt with (given the conditions). I'm sure I could have pushed the settings on the GPX and improved the target response also.

My mistake on calling it low tone when it should have been low conductivity.

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Gosh... DB and nvchris...Just a thought: according to the first post the N Nevada area

was not in the usual volcanics. The bedrock was limestone. No mention of the overburden.

The gb was at 7. At this point I do wonder if what would be if as an experiment the gb

was turned off. In my experence some of the areas I have been hunting gb is not needed

while using the 12-inch dual. I have one of the original "hole" TDI's which should not

make a difference with the later TDI's. I'm not trying to be "picky." This thread has

great information. Both doug and JP are in Australia and can add new tricks and tips

to the pot... To me it is not important which machine is used... it is how to get the

best out of the one in your hand.... "Tailgate" Jim Straight

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